A genomic clone for an alcohol dehydrogenase (Adh) gene has been isolated from Petunia hybrida cv. V30 by screening a Petunia genomic library with a maize Adh1 probe. A combination of RFLP and allozyme segregation data failed to demonstrate which of two Adh loci, both of which map to chromosome 4, was the source of the cloned gene. The product of the cloned genes has been identified unequivocally by a transient expression assay in Petunia protoplasts. We have designated this gene Petunia Adh1. The expression of this gene is tightly regulated in the developing anther, where its gene product is the predominant ADH isozyme. It is anaerobically inducible in roots, stems and leaves of seedlings. The induction of enzyme activity is correlated with induction of Adh1 mRNA.